Friction stir welding of nuclear grade SA508Gr.3Cl.1 and SS304LN dissimilar steels

The present work has been carried out to justify the feasibility of dissimilar metal welds between nuclear grade SA508Gr.3Cl.1 ferritic steel and SS304LN stainless steel using friction stir welding. The evaluation has been made by analysing the metallurgical and mechanical properties of the friction stir welded dissimilar joint. Martensite formation and chemical variations in the weld nugget have been confirmed with optical microscopy, micro-hardness measurement and X-ray diffraction. The resultant chemistry variations owing to solid-state mixing on metallurgical and associated mechanical properties are significant. Transverse tensile tests and Charpy impact tests suggest the required strength of the joint. The tensile specimens were fractured from the SS304LN side, and similar sections of stainless steel have been torn with severe plastic deformation. The significant formation of martensite has not shown any adverse effect on the joint properties. The tool wear rate of tungsten carbide was high for this dissimilar weld.